Curl_http_done: called premature

Question

I'm building a new service, and when I curl it I see a message Curl_http_done: called premature. I can't find any documentation on what it means and am wondering if my service is not conforming to some http spec?

➜  ~ git:(master) ✗ curl localhost:6764/health -vv
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 6764 (#0)
> GET /health HTTP/1.1
> Host: localhost:6764
> User-Agent: curl/7.51.0
> Accept: */*
>
< HTTP/1.1 200 OK
< content-encoding: application/json
< content-length: 16
< connection: close
<
{"status":"ok"}
* Curl_http_done: called premature == 0
* Closing connection 0

Answer 1

Curl_http_done: called premature == 0 was just a debug message, it served no real purpose for ordinary humans, only to libcurl developers...

It was removed in curl 7.53.0 (released Feb 22 2017)

(The debug output told if the transfer ended "naturally" or if something made it it end before it was originally intended to. So the premature would be 1 on such errors and 0 if everything was fine.)